MPG to L/100km: The Complete Fuel Economy Conversion Guide (2026)
Published on 2026-05-18
Why Fuel Economy Conversions Matter in 2026
If you've ever shopped for a car, browsed international vehicle listings, or compared fuel ratings on a road trip abroad, you've run into one of the most confusing unit conversions in everyday life: converting between miles per gallon (MPG) and liters per 100 kilometers (L/100km).
The United States, United Kingdom, and a handful of other countries use MPG to rate fuel economy, while most of the world — including Canada, Europe, Australia, and China — uses L/100km. The two scales measure the same thing (fuel efficiency) but in fundamentally different ways, and the relationship between them is not a simple linear conversion.
In this guide, we'll break down exactly how to convert between these two systems, explain why the math works the way it does, and give you practical reference points for comparing vehicles.
Understanding the Two Scales
Miles Per Gallon (MPG) — "How far can I go?"
MPG answers the question: How many miles can I drive on one gallon of fuel? A higher number means better fuel economy. A car rated at 40 MPG is more efficient than one rated at 25 MPG.
There are actually two different MPG standards:
- US Gallon (3.785 liters): Used in the United States and Latin America.
- Imperial Gallon (4.546 liters): Used in the United Kingdom and some Commonwealth countries.
This distinction matters. A car rated at 40 MPG (Imperial) is actually significantly more efficient than one rated at 40 MPG (US), because the imperial gallon is about 20% larger. Always check which gallon standard is being used.
Liters Per 100 Kilometers (L/100km) — "How much fuel do I use?"
L/100km answers the opposite question: How many liters of fuel does my car consume to travel 100 kilometers? A lower number means better fuel economy. A car rated at 6.0 L/100km is more efficient than one rated at 9.0 L/100km.
This is an "inverse" measurement compared to MPG. That's why the conversion between the two isn't straightforward — as MPG goes up, L/100km goes down, but not in a linear fashion.
The Conversion Formula
US MPG to L/100km
The formula to convert US MPG to L/100km is:
L/100km = 235.215 ÷ MPG (US)
Where does 235.215 come from? It's the combination of two conversion factors: 3.785 liters per US gallon and 1.609 kilometers per mile, calculated as (3.785 × 100) ÷ 1.609 = 235.215.
Imperial MPG to L/100km
For UK/imperial gallons, the formula is slightly different:
L/100km = 282.481 ÷ MPG (Imperial)
L/100km to US MPG
To go the other direction:
MPG (US) = 235.215 ÷ L/100km
Quick Reference Conversion Table
| US MPG | L/100km | Vehicle Type (Approximate) |
|---|---|---|
| 15 MPG | 15.7 L/100km | Large truck / SUV |
| 20 MPG | 11.8 L/100km | Mid-size SUV |
| 25 MPG | 9.4 L/100km | Mid-size sedan |
| 30 MPG | 7.8 L/100km | Compact car |
| 35 MPG | 6.7 L/100km | Efficient compact |
| 40 MPG | 5.9 L/100km | Hybrid vehicle |
| 45 MPG | 5.2 L/100km | Efficient hybrid |
| 50 MPG | 4.7 L/100km | Plug-in hybrid / EV equivalent |
| 55 MPG | 4.3 L/100km | Top-tier hybrid |
| 60 MPG | 3.9 L/100km | Electric vehicle equivalent |
Why the Relationship Isn't Linear
Here's where it gets interesting. Because MPG and L/100km have an inverse relationship, equal steps in MPG don't produce equal steps in L/100km.
For example:
- Improving from 10 to 20 MPG saves 11.8 L/100km (from 23.5 to 11.8).
- Improving from 20 to 30 MPG saves only 4.0 L/100km (from 11.8 to 7.8).
- Improving from 30 to 40 MPG saves only 1.9 L/100km (from 7.8 to 5.9).
This is why going from a 10 MPG truck to a 20 MPG SUV saves dramatically more fuel than going from a 30 MPG sedan to a 40 MPG hybrid — even though both are "10 MPG improvements." The first improvement cuts fuel consumption in half, while the second only reduces it by about 24%.
This counterintuitive reality is sometimes called the "MPG illusion," and it's important to understand when evaluating the real-world impact of fuel economy improvements.
Practical Examples
Example 1: Comparing a US car to a European car
You're looking at a US-market car rated at 32 MPG (US) and a European car rated at 7.5 L/100km. Which is more fuel efficient?
Converting 32 MPG to L/100km: 235.215 ÷ 32 = 7.35 L/100km
The US car at 32 MPG (7.35 L/100km) is slightly more efficient than the European car at 7.5 L/100km.
Example 2: Converting a UK car rating
A British car magazine rates a vehicle at 52 MPG (Imperial). What is that in L/100km?
282.481 ÷ 52 = 5.43 L/100km
That's excellent fuel economy by any standard — typical of a modern diesel or hybrid vehicle.
Example 3: Calculating fuel cost for a road trip
You're planning a 500-kilometer road trip in Europe. Your rental car is rated at 6.5 L/100km, and fuel costs €1.80 per liter. How much will you spend on fuel?
Total fuel needed: 6.5 × (500 ÷ 100) = 32.5 liters
Total cost: 32.5 × €1.80 = €58.50
What if you found a more efficient car rated at 5.0 L/100km?
Total fuel needed: 5.0 × 5 = 25.0 liters
Total cost: 25.0 × €1.80 = €45.00
The more efficient car saves you €13.50 on a single 500 km trip — a meaningful difference over a two-week vacation.
US vs. Imperial MPG: Don't Get Caught Out
One of the most common mistakes in fuel economy comparisons is mixing up US and imperial gallons. Here's a direct comparison:
| Vehicle Efficiency | US MPG | Imperial MPG | L/100km |
|---|---|---|---|
| Gas guzzler | 15 MPG | 18.0 MPG | 15.7 |
| Average SUV | 22 MPG | 26.4 MPG | 10.7 |
| Efficient sedan | 35 MPG | 42.0 MPG | 6.7 |
| Hybrid | 50 MPG | 60.1 MPG | 4.7 |
Notice that the imperial MPG number is always about 20% higher than the US MPG number for the same actual fuel consumption. If you see a UK review claiming 60 MPG, that's roughly equivalent to 50 US MPG — still excellent, but not as dramatic as it might first appear to American readers.
Electric Vehicles and MPGe
Electric vehicles (EVs) complicate things further. The EPA rates EVs in MPGe (miles per gallon equivalent), where 1 gallon of gasoline is considered equivalent to 33.7 kilowatt-hours (kWh) of electrical energy.
A typical EV might be rated at 120 MPGe. Converting that to L/100km equivalent:
235.215 ÷ 120 = 1.96 L/100km equivalent
Of course, EVs don't use liters of gasoline at all — but this equivalent rating allows direct comparison with conventional vehicles. In real-world energy terms, that 120 MPGe EV uses about 28 kWh per 100 km, which at $0.15/kWh costs only about $4.20 per 100 km — far less than any gasoline vehicle.
Convert Any Unit Instantly
Need to convert MPG, L/100km, or any other unit? Our free unit converter handles fuel economy, distance, volume, and more — with precision to two decimal places.
Try the Unit ConverterFrequently Asked Questions
1. How do I convert MPG to L/100km?
Divide 235.215 by the US MPG value (or 282.481 by the Imperial MPG value). For example, 30 US MPG = 235.215 ÷ 30 = 7.84 L/100km.
2. Is US MPG the same as UK MPG?
No. The US gallon is 3.785 liters, while the UK (imperial) gallon is 4.546 liters. A car rated at 40 MPG in the UK is actually more efficient than one rated at 40 MPG in the US. To convert: multiply US MPG by 1.201 to get Imperial MPG.
3. Why does Europe use L/100km instead of MPG?
L/100km is considered more intuitive for most consumers because it directly tells you how much fuel you'll use for a given distance. This makes it easier to calculate fuel costs for a trip. MPG tells you how far you can go on one unit of fuel, which is useful but less direct for cost planning.
4. What is a good MPG rating in 2026?
For a conventional gasoline car, anything above 35 MPG (US) is considered good. Hybrids typically achieve 45-55 MPG, and plug-in hybrids can exceed 100 MPGe when combining electric and gasoline operation. For reference, 35 MPG equals about 6.7 L/100km.
5. How does MPGe compare to real-world EV efficiency?
MPGe is a standardized rating that allows comparison between EVs and gasoline vehicles. A car rated at 100 MPGe uses 33.7 kWh per 62 miles (100 km). Real-world efficiency varies with driving conditions, temperature, and speed, but MPGe provides a consistent baseline for comparison.
6. Can I use these conversions for motorcycles and scooters?
Yes. The same formulas apply regardless of vehicle type. A motorcycle rated at 60 MPG (US) converts to 235.215 ÷ 60 = 3.92 L/100km. Small scooters can achieve 80-100 MPG (US), which equals roughly 2.4-2.9 L/100km.
Whether you're comparing cars across international markets, calculating fuel costs for a trip, or simply trying to understand what a European car review means in terms you're familiar with, mastering the MPG to L/100km conversion is an essential skill in our increasingly connected world. Bookmark this page and use our converter tool whenever you need a quick, accurate answer.